Evidence exists which implicates an immunologic mechanism in the pathogenesis of pulmonary fibrosis. Whether the immune response is a major contributor in the pathogenesis of pulmonary fibrosis or is just a secondary manifestation of lung injury is not known. The purpose of this proposal is to further investigate the role of immune mechanisms the pathogenesis of diffuse fibrosing pulmonary disorders. A blemoycin animal model pulmonary fibrosis which morphologically and physiologically resembles human diffuse pulmonary fibrosis will be used. Lymphocyte populations will be characterized and isolated from the lungs of bleomycin animals at various stages of the fibrotic mechanism. The effect of these immune cells and their supernates upon fibroblast growth, collagen synthesis (total collagen and ratio of type I to type III) and prostaglandin elaboration will be studied. Since in vivo experiments in our laboratory have shown that thymectomized animals and animals treated with indomethacin, methylprednisolone, cobra venom factor and antilymphocyte globulin have a suppressed fibrotic response in this animal model system, we will also study immune cell populations from these treated animals to see if their effect on fibroblast activity is different from untreated animals. Mononuclear cells will be purified from spleen, bronchoalveolar lavage and lung from both normal animals and animals at various times during the development of bleomycin-induced pulmonary fibrosis. With the use of specific antibodies to subpopulations of lymphocytes and the fluorescence activated cell sorter the following populations of mononuclear cells will be isolated: macrophages (normal and post bleomycin), B-cells and their subpopulations (Thyl+, Ig+ and Thyl-, Ig+), T-cells and their subpopulations (helper cell activity - W3/25+ cells and suppressor cell activity - 0X8+ cells). The effect of supernates obtained from short term culture of these purified cell populations on fibroblasts cultured from normal lungs and lungs at various stages during the development of pulmonary fibrosis will be studied. The cultured mononuclear cells will be studied under three conditions: 1) unstimulated, 2) stimulated with nonspecific agents (mitogens, bleomycin), and 3) stimulated with specific antigens (type I and III collagen). The significance of this proposal lies in its direct approach to analyze whether immune cells can directly influence fibroblast activity.